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VIII. On the Vertebral Characters of the Order Pterosauria, as exemplified in the Genera 
Pterodactylus (Cm^ER) and Dimorphodon (Owen). By Professor Owen, F.B.S., 
Superintendent of the Natural History Departments in the British Museum. 
Eeceived Eebruary 23, — Bead March 24, 1859. 
Although the skeletons of the extinct Flying Sanrians of the mezozoic strata have been 
discovered in a more complete condition than those of any other contemporary Eeptiles, 
they have not, hitherto, owing to the delicate texture and commonly crushed state of 
the bones, afforded satisfactory observations of the structure of the vertebrae. Yet the 
vertebral characters of a saurian skeleton are of peculiar interest to the Palaeontologist 
and Comparative Anatomist, on account of the many and strongly-marked differences 
which they present in the extinct members of the Keptihan class. 
In the existing species, the articular terminal surfaces of the centrum, with the excep- 
tion of those of the Geckos, Ehynchocephalus * * * § , and of some single vertebrae in the 
column of other Reptiles f, are concave in front and convex behind. But in extinct Rep- 
tiles some genera {Streptospondylus) show reverse positions of the cup and ball ; others 
{Ichthyosaurus) show both surfaces concave ; others show both surfaces slightly concave 
{Teleosaurus) ; others show both surfaces flat (some Plesiosauri) ; others are subconcave 
behind and flat before {Cetiosaurus) ; -with many minor modifications. It is only on 
arriving at the uppermost of the mezozoic series of rocks in an ascending survey, that 
we find Lacertian genera {Mosasaurus and Leiodon% of the Chalk) and crocodilians 
{Crocodilus hasifissus, from the Greensand of New Jersey §) presenting the proccelian || 
type of vertebra which prevails in tertiary and modern reptiles. 
No fossil vertebra from secondary rocks has come under my observation or know- 
ledge with characters of the articular ends of the centrum which distinguish the verte- 
brae of bu’ds, viz. a concavity in one direction and a convexity in the other, the directions 
being reversed at the two ends of the centrum. 
All the foregoing considerations have tended to invest the question of the vertebral 
characters of the Pterodactyles with peculiar interest ; and, especially, seeing the adapta- 
* Catalogue of the Osteological Series, Museum of the Eoyal College of Surgeons, 4to. 1853, p. 142. 
t Biconcave fifth cervical vertebra in Chelone Mydas ; biconvex first caudal vertebra. Crocodile. — Cata- 
logue of the Physiological Series, Museum of the Eoyal College of Surgeons, 4to. vol. i. 1832, pp. 52, 53. 
X History of British Possil Eeptiles, 4to. p. 188. 
§ “ Notes on Ee mains of Possil Eeptiles discovered in Greensand Pormations of New Jersey,” Quarterly 
Journal of the Geological Society, vol. v. 1849, p. 380. 
II Eeport on British Possil Eeptiles, 8vo. 1841, p. 65. 
MDCCCLIX. Z 
